One of conventional three-phase power conversion devices converts DC power of a distributed power supply such as a solar battery to three-phase-output AC power and outputs the AC power to a load. This conventional three-phase power conversion device includes a three-phase 3-level inverter connected between positive and negative terminals of a first DC power supply, and one or a plurality of single-phase inverters which receive smaller DC voltage than voltage of one level of the three-phase 3-level inverter and are connected in series to an AC output line for each phase of the three-phase 3-level inverter. Each phase of the three-phase 3-level inverter outputs one pulse of voltage per half cycle of voltage for each phase outputted to the load. Each single-phase inverter performs output by PWM control, and a sum of output voltage of the three-phase 3-level inverter and output voltage of each single-phase inverter is outputted via a smoothing filter to the load. Each single-phase inverter performs output based on an output voltage command obtained by superimposing zero-phase voltage common to the three phases, onto difference voltage for each phase obtained by subtracting output voltage for each phase of the three-phase 3-level inverter from sine wave voltage for each phase. The zero-phase voltage common to the three phases is calculated by inverting the polarity of average voltage obtained by averaging the maximum value and the minimum value among the difference voltages for these phases at each point of time (for example, see Patent Document 1).